Insight into the mechanism of hydrogen permeation inhibition by cerium during electroplating: Enhanced kinetics of hydrogen desorption

In our previous work, we found that hydrogen permeation can be noticeably reduced during Ni–Cu electroplating by the addition of Ce salt to the plating solution. The mechanism of hydrogen permeation inhibition via Ce salt was further studied in the present work. Through the Iver–Pickering–Zamenzadeh (IPZ) model fitting of the kinetic of hydrogen evolution reaction, we found that the trace Ce salt that precipitated during electroplating could improve Tafel reaction kinetic parameters and reduce the strength of the Ni–H and Cu–H bonds due to its abundant d/f electrons and enough d/f orbitals. Meanwhile, Ce can provide electrons for the Heyrovsky reaction. These effects promoted surface electron migration and thus led to the desorption of adsorbed hydrogen atoms (H_ads) and the decreased diffusion of H_ads into the Ni–Cu coatings. The accuracy of the IPZ model fitting results was verified by hydrogen evolution rate experiments during the electroplating process. Hence, Ce salt can effectively inhibit hydrogen permeation and reduce the dehydrogenation annealing time, thereby showing great potential for energy saving and emission reduction in the electroplating industry.